Embodiments of the present invention relate to a thin film transistor liquid crystal display (TFT-LCD) array substrate, a manufacturing method thereof and a liquid crystal display panel.
In forming an array substrate of a horizontal electric field type TFT-LCD, a transparent conductive film is first deposited on a transparent substrate to form a common electrode, and then a pixel electrode is formed on the substrate. The electric field parallel to the transparent substrate is generated between the pixel electrode and the common electrode, and the liquid crystal molecules rotate in the plane parallel to the transparent substrate under the above electric field. The non-overlapping portion, between the pixel electrode and the common electrode forms liquid crystal capacitance, and the overlapping portion between the pixel electrode and the common electrode forms storage capacitance to maintain the voltage on the pixel electrode.
Feed through may be generated during the process of applying a voltage to the pixel electrode. The voltage of the feed through is expressed as follows: Δv=(Δgate·Cgd)/(Cgd+Cst+Clc), where Δv is the feed through voltage, ΔGate is the gate voltage of the TFT as a switching element, Cgd is the capacitance generated by the overlapping portion between the gate electrode and the drain electrode of the TFT; Cst is the storage capacitance between the pixel electrode and the common electrode, and Clc is the liquid crystal capacitance between the pixel electrode and the common electrode. The voltage applied on the pixel electrode is reduced due to the feed through voltage.
The reversion of the liquid crystal molecules is accomplished by the voltage difference between the pixel electrode and the common electrode. In order to retard the aging of the liquid crystal molecules, the voltage difference on both sides of the liquid crystal molecules between adjacent frames is reversed. During the display of the image, the discontinuity of the image brightness is generated between adjacent frames due to the drop of the pixel electrode voltage. FIG. 13 is a diagram showing the occurrence of the feed through voltage on the pixel electrode of a conventional TFT-LCD array substrate.
During the period of the n-th frame, the signal 11 input to the gate electrode at the initial stage is at a high level, the TFT in the pixel region is turned on, and the signal 12 input to the data line is conducted to the pixel electrode through the TFT. At the same time, the voltage of the signal 13 input to the pixel electrode is larger than that of the signal 14 input to the common electrode. Compared with the signal 12 input to the data line, the signal 13 input to the pixel electrode is decreased due to the existence of feed through. Thus, the voltage difference between the signal 13 input to the pixel electrode and the signal 14 input to the common electrode is smaller than the desired voltage difference, that is, the voltage difference applied on both sides of the liquid crystal molecules is smaller than the desired voltage difference.
During the period of the (n+1)-th frame display, the signal 11 input to the gate electrode at the initial stage is at a high level, the TFT in the pixel region is turned on, and the signal 12 input to the data line is conducted to the pixel electrode through the TFT. At the same time, the voltage of the signal 13 input to the pixel electrode is smaller than that of the signal 14 input to the common electrode. Compared with the signal 12 input to the data line, the signal 13 input to the pixel electrode is decreased due to the feed through. Thus, the voltage difference between the signal 13 input to the pixel electrode and the signal 14 input to the common electrode is larger than the desired voltage difference, that is, the voltage difference applied on both sides of the liquid crystal molecules is larger than the desired voltage difference. Therefore, the discontinuity of the voltage difference applied on both sides of the liquid crystal molecules is generated between two adjacent frames.